25. Cooperation with MPI

25.1. Calling MPI program from XMP program

You can call the MPI program from the XMP program by using the following functions.

• Initialization of MPI environment

Language	Retrun Value	Function
XMP/C	void	xmp_init_mpi(int*, char***)
XMP/Fortran	(None)	xmp_init_mpi()

• Acquisition of MPI Communicator for node set

Language	Retrun Value	Function
XMP/C	MPI_Comm	xmp_get_mpi_comm(void)
XMP/Fortran	integer	xmp_get_mpi_comm()

• Finalization of MPI environment

Language	Retrun Value	Function
XMP/C	void	xmp_finalize_mpi(void)
XMP/Fortran	(None)	xmp_finalize_mpi()

• XMP/C program

#include <mpi.h>
#include <xmp.h>
#pragma xmp nodes p[4]

int main(int argc, char **argv) {
  xmp_init_mpi(&argc, &argv);
  int rank, size;
  MPI_Comm_rank(MPI_COMM_WORLD, &rank);
  MPI_Comm_size(MPI_COMM_WORLD, &size);

#pragma xmp task on p[1:2]
{
  MPI_Comm comm = xmp_get_mpi_comm();
  MPI_Bcast(..., comm);
}
  xmp_finalize_mpi();

  return 0;
}

• XMP/Fortran program

program main
  include 'mpif.h'
  integer rank, irank, isize, ierr
  integer xmp_get_mpi_comm
  integer comm

!$xmp nodes p(4)
  call xmp_init_mpi()

!$xmp task on p(2:3)
  comm = xmp_get_mpi_comm()
  call MPI_Bcast(..., comm, ...)
!$xmp end task

  call xmp_finalize_mpi()
end program

The xmp_init_mpi() initializes the MPI environment with the XMP program, and the xmp_finalize_mpi() performs the completion processing of the MPI environment with the XMP program. You can call any MPI functions and the xmp_get_mpi_comm() between the above two functions. The xmp_get_mpi_comm() can acquire the MPI communicator of the node set (p[1:2] in the above XMP/C and p(2:3) in the XMP/Fortran) currently being executed.

25.2. Calling XMP program from MPI program

You can call the XMP program from the MPI program by using the following functions.

• Initialization of XMP environment

Language	Retrun Value	Function
XMP/C	void	xmp_init(MPI_Comm)
XMP/Fortran	(None)	xmp_init(Integer)

• Finalization of XMP environment

Language	Retrun Value	Function
XMP/C	void	xmp_finalize(void)
XMP/Fortran	(None)	xmp_finalize()

• MPI/C program

#include <mpi.h>
#include <xmp.h>
extern void xmp_sub();

int main(int argc, char **argv)
{
  MPI_Init(&argc, &argv);
  xmp_init(MPI_COMM_WORLD);

  sub_xmp();

  xmp_finalize();
  MPI_Finalize();

  return 0;
}

• XMP/C program

void sub_xmp() {
#pragma xmp nodes p[4]
   :
}

• MPI/Fortran program

program test
  include 'mpif.h'
  integer ierror

  call MPI_INIT(ierror)
  call xmp_init(MPI_COMM_WORLD)
  call xmp_sub()
  call xmp_finalize()
  call MPI_FINALIZE(ierror)

end program test

• XMP/Fortran program

subroutine sub_xmp()
!$xmp nodes p(4)
   :
end subroutine hoge

The xmp_init() initializes the XMP environment with the MPI program, and the xmp_finalize() completes the XMP environment with the MPI program. You can call any XMP functions can be called between the above two functions. Note that, the xmp_init() must be executed after the MPI_Init() and the xmp_finalize() must be executed before the MPI_Finalize().